Objective: To characterize the humoral immune response to islet antigen 2 (IA-2) in patients with newly diagnosed type 1 diabetes (T1D), we compared the profile of epitope-and isotype-specific IA-2 antibodies (IA-2A) between children with a humoral immune response restricted to IA-2 and children with a broad response including insulin autoantibodies (IAA) and antibodies to glutamic acid decarboxylase (GADA) in addition to IA-2A. Methods: The study subjects (nZ100) were derived from a consecutive series of 1108 patients from the Finnish Pediatric Diabetes Register (investigators listed in the Appendix). Islet cell antibodies, IAA, GADA, total IA-2A levels, IA-2/IA-2b epitopes, and isotypes were measured, and human leukocyte antigen (HLA) genotypes were analyzed. Results: There were no significant differences between the two groups in the frequency or levels of epitope-specific IA-2A. Those with an IA-2-restrictive response tested positive more frequently for IgA-IA-2A (PZ0.001), had higher titers of IgE-IA-2A (PZ0.025), tested positive for more IA-2A isotypes than the broad responders (PZ0.04), and carried the high-risk HLA-(DR4)-DQB1*0302 haplotype more frequently than those with a broad antibody response (PZ0.019). Conclusions: These data show that children with newly diagnosed T1D, who test positive only for IA-2A out of the three molecular antibodies predictive of T1D, have a broader IA-2-specific isotype response and stronger association with the high-risk HLA haplotype than those testing positive for all three molecular antibodies. This may be indicative of a different pathogenetic mechanism in those with their humoral immune response restricted to IA-2 at the time of diagnosis.